Berkeley Sockets

Berkeley sockets is an application programming interface (API) for Internet sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated with the 4.2BSD Unix released in 1983.

A socket is an abstract representation (handle) for the local endpoint of a network communication path. The Berkeley sockets API represents it as a file descriptor (file handle) in the Unix philosophy that provides a common interface for input and output to streams of data.

Berkeley sockets evolved with little modification from a de facto standard into a component of the POSIX specification. Therefore, the term POSIX sockets is essentially synonymous with Berkeley sockets. They are also known as BSD sockets, acknowledging the first implementation in the Berkeley Software Distribution.

Berkeley sockets originated with the 4.2BSD Unix operating system (released in 1983) as a programming interface. Only in 1989, however, could UC Berkeley release versions of its operating system and networking library free from the licensing constraints of AT&T Corporation's proprietary Unix.

All modern operating systems implement a version of the Berkeley or POSIX socket interface. It became the standard interface for connecting to the Internet. Even the Winsock implementation for MS Windows, developed by unaffiliated developers, closely follows the standard.

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